350 THE FORK-TAILED DATE-SHELL. 



fully strong, silken in their texture, and, had the mollusk been sufficiently plentiful, might 

 have been employed in various manufactures. I have seen a pair of gloves that have been 

 woven from the byssus of the giant Pinna, a species which sometimes attains the length of two 

 feet, and has a most singular appearance when old, owing to the mass of parasitic creatures, 

 such as serpulae, balani, and sundry zoophytes, that always congregate on such substances. 



It is remarkable that a little crab, called, from its habits, Pinnotheres, is often found 

 within the shell of this mollusk, and was formerly thought to have entered into a tacit agree- 

 ment with its host' to act as sentinel and to bring in food as a return for the hospitality afforded 

 to it. This, however, is not a solitary instance of such strange alliance, several other mollusks 

 being known to shelter their particular crustacean guest. When at rest, the Pinna is mostly 

 buried in the sand, with the exception of the upper edges of the shell, which are permitted to 

 protrude just above the substances in which the rest of the creature is immersed. 



WE now come to the large, useful, and even beautiful family of the Mussels, although, in 

 most cases, their beauty is not perceptible until the shell has been polished and the rich tints 

 thereby brought out. Rough and polished mahogany are not more unlike each other than the 

 Mussel-shell before and after the polishing process. Some species are marine, while others 

 inhabit the fresh water, and all may be known by the peculiar shape of the shells. 



The EDIBLE MUSSEL, so common in the fishmonger's shop and the costermonger's barrow, 

 is found in vast profusion on European coasts, where it may be seen moored to rocks, stones, 

 and fibres, alternately covered with water or left dry, according to the flowing and ebbing of 

 the tide. The heedless bather is sometimes apt to come unexpectedly upon a collection of 

 these mollusks, and if he once meets with that misfortune, his lacerated limbs, cut in all 

 directions by the knife-like edges of the shells, will serve as effectual warnings not to repeat 

 the same imprudence. 



At some periods of the year the Mussel is extremely injurious as an article of food, though 

 the effects seem, like those produced by eating the bonita, to depend greatly on the constitution 

 of the partaker, some being able to eat it with impunity, while others who have shared the 

 same meal are visited with asthma, violent rash, nausea, and many other symptoms which, 

 though not absolutely dangerous, are peculiarly annoying. The Mussel is largely used for 

 bait as well as for human consumption, more than thirty millions being collected annually in 

 one locality for that purpose. Little, ill-shapen and badly-colored pearls are often found 

 in this mollusk, but are quite useless for the market. Attempts have been successfully made 

 to propagate the breed of Mussels ; and the vast plantations, as they may be called, of these 

 creatures have increased to such an extent, that they threaten to obliterate several useful bays 

 for all maritime purposes. 



An allied species, the DREISSENA, inhabiting the fresh waters, has of late years rapidly 

 overrun England, having been originally imported into the Surrey Docks, whence it has spread 

 with astonishing fertility, passing from one river to another, getting into all the little rivulets 

 that trickle between meadows, and even obtaining entrance into artificial basins by means of 

 the water that feeds them through pipes. The shell is like that of the edible Mussel, but 

 shorter, and without the beautiful nacreous lining. 



THE FORK-TAILED DATE-SHELL is a little, ochre-colored shell, without any peculiar beauty 

 of form or color, but yet as remarkable a creature as any that has been or will be mentioned. 



This little being has the power of burrowing deeply into the hardest stone. I know an 

 instance where the substance in which the Lithodomi were imbedded was a shell of the gigantic 

 limpet from Madagascar, measuring about six inches in diameter and half an inch or so in 

 thickness. This specimen, which I have carefully examined, was a really wonderful one, the 

 thick, hard, and solid substance of the shell being literally riddled with the holes of the Litho- 

 domus, whose forked processes projected from the circular aperture much like the eggs of the 

 common scatophagus from the substance in which they are sunk. 



The method by which this little mollusk contrives to excavate its chamber is a complete 

 mystery. It is known that in its earlier stages it spins a byssus, and attaches itself to 



